describe("Double", function() {
  var func=tab;
  
  it("f(0) = 0", function() {
    var input = 0;
    var output = 0;
    expect(func(input)).toBe(output);
  });
  
  it("f(1)=1", function() {
    var input = 1;
    var output = 1;
    expect(func(input)).toBe(output);
  });
});
